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21 Cards in this Set

  • Front
  • Back
(general properties)
(-) ssRNA, segmented
3 genera: Influenzavirus A/B/V
3 types: Influenza A/B/C virsu
(-) ssRNA, SEGMENTED genome
Types A/B have 8 segments
Type C has 7 segments (lacks component encoding NA)
Influenza A Virus
Genera: Influenzavirus A
Family: Orthomyxoviridae
Influenza A Virus
(important viral proteins)
Hemagglutinin (attaches to cellular receptor, sialic acid)
Neuraminidase (important for viral release)
Nucleoprotein (imp. serology)
Influenza A/B/C Virus and Genomes
All (-) ssRNA and SEGMENTED
A/B have 8 segments
C has 7 segments
Encode different # proteins
A = 10, B = 11, C = 9
* C lacks Neuraminidase
Influenza A Virus
Enveloped, with NA and HA glycoprotein spikes
Matrix protein lines inside of envelope
8 RNP (ribonucleoproteins) are anchored to the matrix protein
Influenza A Virus
(mechanism of replication)
HA binds cell surface sialic acid
M2 H+ channel enables RNP to be released from internal matrix
Low pH causes envelope membrane to fuse with endosome membrane, spilling newly released RNPs to cytoplasm where they target to nucleus for replication
Assembly of virion occurs at cytoplasm
NA enables release of newly synthesized and budding virions
(primary symptoms)
Febrile respiratory illness
Sudden onset + systemic symptoms (headache, muscle ache, malaise, cough)
Fever + "severe symptomos" < 1 week
Muscle aches + malaise: 1 - 2 weeks
What is the most common, serious complication of acute influenza?
Pneumonia, due to
(1) primary influenza virus
(2) Mixed viral-bacterial (staph)
(2) post influenza bacterial* (pneumococcal)
In addition to pneumonia, what are some other complications due to influenza infection?
Otitis Media
Reye's Syndrome (encephalitis + impaired liver function, exacerbated by aspirin)
Encephalitis (rare)
(clinical diagnosis)
Symptoms: cough and myalgia
Community: widespread problem? winter months? etc
(laboratory diagnosis)
Rapid Antigen Test (ELISA, immunofluorescence, NA enzyme activity)
Virus isolation
Serology (look for Ab rise between acute and convalescent sera)
Influenza Classification
(antigen characterisitcs)
Types based on STABLE nucleoprotein antignes (A/B/C are FIXED classifications)
HA/NA (of type A) are variable, and lead to subclass designation (i.e. H1/2/3 and N1/2 etc) when antisera fails to bind test antigens - antigen shift
Antigen Shift
Gives rise to pandemic flu
Due to reassortment of RNP segments (think coinfection of swine and human flu - might mix/match genome, giving rise to a new more virulent strain)
Antigen Drift
Subtle changes in RNA that may increase epidemic prevalence but are not responsible for pandemic illnesses
Highest infection rate: school-age children, followed by pre-schoolers and adults of all ages
IgG antibody of lower respiratory tract secretions (from serum). Therefore, Ab titer closely correlates w/immunity. IgA predominates in upper respiratory tract secretions and also contributes to immunity (though less persistent)
(Ab to HA vs. NA)
Anti-HA antibody prevents infection
Anti-NA antibody lessens severity
(antiviral therapy)
M2 inhibitors
Neuraminidase Inhibitors
M2 inhibitors
Recall: M2 is the protono channel required to release RNPs from M1 matrix protein
W/out release, RNPs cannot shuttle to nucleus for replication
Cons: early resistance and does not work against type B
Neuramidase Inhibitors
Work against type A/B influenza
Low resistance